In the Legacy Transmission Control Protocol (TCP)/Internet Protocol (IP) network environment, the IP provides routing functionality to the Internet. The IP allocates logical addresses, that is, the IP addresses, to all the nodes (including hosts and routers), and each port of every host is allocated an IP address. The IP address comprises a network prefix and a host part, and the IP addresses of all the hosts in the same one link usually have the same network prefix and different host parts, which makes the IP able to select the routing based on the network prefix part of the destination node's IP address, so that the router only keep a simple network prefix routing and does not need to save a separate routing for each host. In this case, since the network prefix routing is used, when the node switches from one link to another without changing its IP address, the node cannot receive data messages in the new link, thus can not communicate with other nodes.
Legacy IP networks do not support endpoint mobility, and the existing technology proposes various solutions, mainly comprising the Mobile IPv4, the Mobile IPV6, and the proxy mobile IPV6 (also abbreviated as PMIPv6) of the Internet Engineering Task Force (IETF), and the way of General Packet Radio Service technology (GPRS) Tunneling Protocol (GTP) of the Third Generation Partnership Project (3GPP) and so on. The existing technology uses the way of fixed anchor points to support the endpoint mobility, for example, the wideband code division multiple access (WCDMA) specifies the Gateway GPRS Support Node (GGSN) as the mobile anchor point of the endpoint; the code division multiple Address (CDMA) network uses the Mobile IP protocol to take the home agent (HA) as the anchor point. However, the fixed anchor point brings the issue of circuitous path of data packets, increases the transmission delay and bandwidth waste. With the development of the 2G/3G/4G wireless packet technologies, the number of mobile Internet users and traffic gradually increase, and gateway devices such as GGSN gradually switch downwards, which makes the problem of circuitous path even worse.
Both the Mobile IPV4 and the Mobile IPV6 are endpoints based mobility solutions that are characterized by that the endpoints need to deal with mobility-related processes.
The main problem of the Mobile MIPv4 is circuitous routing, for example, the endpoint A opens an account in the X area, and the corresponding HA is in the X area. The communication peer endpoint B is in the Y area. Even if the A roams to the Y area, its data flow still needs to be sent from the Y area back to the X area, and then sent to the peer endpoint B.
Relative to the MIPV4, the major improvement of the Mobile MIPV6 is that a path optimization process is defined to avoid the circuitous path, but it has the following problems:
1) first, the MIPV6 path optimization process is an end-to-end process, the endpoints should support the Mobile IPV6, but in fact, there are relatively few endpoints supporting the MIPV6, and the fixedly accessed endpoints generally do not support, which makes the MIPV6 path optimization process difficult to implement;
2) a new address should be allocated at each time that a user switches, the address allocation takes a long time, which leads to a large switching delay.
Another type of technology is network-based mobility solutions, including Proxy Mobile IP, 3GPP GPRS Tunneling Protocol (GTP) tunnel, and so on.
The ways of PMIPv6 and the GTP are relatively similar from the routing point of view. The main problem is:
1) there are Local Mobility Anchors (LMA), Packet Data Network Gateway (PGW), or the GGSN, and circuitous routing will be introduced here, and the circuitous routing problem is similar to the MIPV4 in the static IP address allocation method;
2) once the endpoint powers up and is online, it must be anchored to a LMA, PGW, or GGSN, no matter whether it is Local Breakout, dynamically specified LMA or another existing method, and when the endpoint location changes subsequently, the anchor location will not change unless the endpoint is allocated a new address after dropping off and then being online again.
The IP address in the TCP/IP protocol extensively used by the existing Internet has dual function, both as the location identifier of the communication endpoint host network interface in the network layer in the network topology, and as the identity identifier of the host network interface in the transport layer. The TCP/IP protocol design did not consider the host mobility at the very beginning. However, when the host mobility is more and more common, the shortcoming of semantic overload of the IP address is increasingly evident. When the IP address of the host changes, not only the routing but also the identity identifier of the communication endpoint host will change, which leads to increasingly heavy routing load, and the change of the host identifier will lead to the disruption in the applications and the connections.
The purpose of proposing the identity identifier and location separation problem is intended to resolve problems comprising the semantic overload of the IP address and the heavy routing overload and so on, separate the dual function of the IP address and achieve the support of mobility, multiple hosts, IP address dynamic reallocation, routing load reduction and visits among different network areas in the next-generation Internet.
The IP does not support mobility, whose essential reason is that the IP address contains the dual properties of identity and location.
The identity attribute of the IP address is: in the TCP/IP protocol stack, the IP address is used to identify the communication peer endpoint.
The location attribute of the IP address is: the IP address represents which network segment where the user is located, which is the basis for routing.
In the fixed network, there is no problem that the location and the identity attributes of the IP address are combined as one, which is because the endpoint location keeps unchanged, when the IP address will not change, so as the identity attribute.
But to the mobile Internet, the movement of the endpoint location results in that the IP address must be changed, otherwise, the routing can not be implemented; but the change of the IP address leads to the change of the endpoint identity, and the TCP/User Datagram Protocol (UDP) connection must be broken and reconnected, which is unacceptable for most applications. Therefore, the support of the Legacy IP protocol on mobility has fundamental problems.
In the existing technology, there are two main solutions for the identity identifier and location separation, one solution is host-based implementation, and the other is router-based implementation, and each implementation has multiple related technologies to support. The main existing host-based protocol is the host identity protocol (HIP), and the main existing routing-based protocol the location and identity separation protocol (LISP), and so on.
The HIP is a host mobility associated protocol, and the HIP separates the IP address into the endpoint identifier and the location identifier. The basic idea of the HIP is to introduce the 3.5th layer: the Host Identity Layer (HIL) between the network layer (the third layer) and the transport layer (the fourth layer), that is, introducing the Host Identity (HI) space between the domain name space and the IP address space. The Host identifier layer separates the originally tightly coupled transport layer and network layer, and the IP address does not play the role of identifying the host any more, it is only responsible for routing forwarding of the packets, that is, it only works as a locator, the host name is expressed by the host identifier. The host identifier layer is logically located between the network layer and the transport layer, the transport layer uses the transport layer identifier, and the host identifier layer completes the conversion between the host identifier in the data packet and the IP address. The network layer is shielded from the transport layer, and any change of the network layer (for example, the change of the host IP address in the communication process) will not affect the transport layer link, unless the quality of service changes.
Thus, the transport layer connection is established on the host identifier, and the IP address can only be used for the network layer routing but not used to identify the host identity. The key idea of the HIP is to disconnect the tightly coupling between the network layer and the transport layer, so that the connection between the application layer and the transport layer is not affected by the change of the IP address. When the IP address changes in a connection, the HI remains unchanged, thus ensuring that the connection is not interrupted. In hosts supporting the HIP, the IP addresses can only be used for routing and addressing, while the HI is used to identify the endpoint host corresponding to a connection, and replaces the IP address used in the connection socket.
The HIP is a host protocol, whose main problem is: the premise of deployment is that all the endpoints participating in the communication need to synchronously support the HIP, and the endpoints even the upper-layer applications need to be changed substantially. The network does not participate in the management of the user access, and needs to participate in maintaining the communication links in the location update stage when both of the communication endpoints move synchronously, or else, the problem of packet loss will occur. In addition, the HIP cannot implement anonymous communication.
The LISP reuses the routing technology, makes a certain change to the existing routing topology, and optimizes the existing transport technology with the minimal modification when combined with the existing transport network.
The host uses the IP address (called as endpoint identifier (EID) in the LISP system) to track the socket, establish connection, send and receive data packets.
The router transmits data packets based on the IP destination address (called as the routing location (RLOCs) in the LISP system).
The tunneling routing is introduced in the LISP system, and the LISP data packets are encapsulated when initiating the host packets and de-encapsulated before the packets are finally sent to the destination. The IP address of the “outer header” in the LISP packets is the RLOCs. In the end-to-end packet exchange process between hosts in two networks, the ITR (ingress tunneling router) encapsulates each packet with a new LISP header, and the egress tunneling router moves the new header. The ITR implements the EID-to-RLOC inquiry to determine the routing path to ETR (egress tunneling router), and the ETR takes the RLOC as one of its own addresses.
The proposal of the LISP is not for solving the problem of mobility but mainly for solving the problem of network size that is targeted at the problem of the too large routing table, the mobility and multi-host attributes are side problems to be solved after the identifier and location are separated, and there are no specific solutions and implementation methods so far.
In addition, the LISP is a network-based protocol, and only affects the network part, which is more precisely only affecting the existing Internet backbone rather than the access layer and the user hosts in the existing network, and completely transparent to the hosts.
In summary, the existing network technologies have the following shortcomings:
the TCP/IP uses the way of fixed anchors to support the mobility of the endpoint in the prior art, but the fixed anchors bring the issue of circuitous path of the data packets, increase the transmission time-delay and the bandwidth waste. The MIPV6 routing optimization process needs that the hosts participating in communication support the MIPV6 protocol, and the deployment is difficult;
the IP address in the TCP/IP has a dual function: both as the location identifier of the communication endpoint host network interface in the network layer in the network topology, and as the host network interface identity identifier in the transport layer. The identity identifier and location separation frameworks: HIP, LISP, and so on in the prior art are a new network framework constructed to overcome the shortcomings of the existing network technology. The host-based HIP needs to do relatively large modification on endpoints and upper-layer services, and its deployment is difficult; the network is needed to participate in maintain the communication links at the stage when both communication endpoints move simultaneously and the location updates, otherwise, the problem of packet loss will occur. For the network-based LISP, the mobility and multi-host attributes are side problems to be solved after the identifier and location are separated, and there are no specific solutions and implementation methods so far.
The scalability of the routing system is poor, and an important reason causing the routing system scalability in the legacy IP network is the change of the routing table size and the network topology. The main application scenery considered when the Legacy IP network is initially designed is the fixed access mode, and the IP address comprises the network prefix and the host part, and all the hosts in the same link usually have the same network prefix and different host parts. The Legacy IP network uses the network prefix routing, and the change of the network topology will affect the IP address allocation of the endpoint hosts. Under this mechanism, continuously increasing host mobility demand will increase the network topology complexity, leading to the increasing number of routing table entries and the increasing probability of the change of the routing table.